274 I. IJIMA : HEXACTINELLIDA. I. 



The dermalia present tliemselves in sjiecially large size and 

 strong development on the papillœ which as we have seen stand 

 in relation wdth the hydranth of the commensal Hydrozoa, as 

 well as on the free edge of the cuff (PL X, figs. 25-27 ; PL XI, 

 fig. 4). They give to these parts the spiny appearance already 

 mentioned and might not improperly be called prostal hexactins, 

 were it not for the comparatively insignificant length attained by 

 the freely projecting, distal ray. 



On the papillœ (PL XI, fig. 3), the dermalia are sword- 

 shaj^ed hexactins, many times larger than the ordinary dermalia 

 and with the distal ray swollen into a fusiform or a club-like 

 shape (PL X, figs. 18, 25-27). This ray generally measures 

 600-870/^ in length and 45-80 /^- in greatest breadth. Its lateral 

 contours are frequently not symmetrically even. Close to the 

 rounded or bluntly pointed end the surface is rough on account 

 of the presence of either pointed or rounded microtubercles. 

 Sometimes the ray is smooth nearly all over. All tlie other 

 rays (11-27 /-« thick near base) are tapering, subterminally spar- 

 ingly microtubercled, and end couically or obtusely pointed. 

 The paratangentials are comparatively very short and often of 

 unequal length in the same spicule. The long proximal ray, 

 which dips into the parenchyma accompanied with diactin- 

 comitalia, may be 2 mm. or more in length ; occasionally as 

 short as the paratangentials. It is not infrequently more or less 

 distinctly bent in its course. 



From PL X, fig. 22, or by comparing figs. 23-24 with figs. 

 25-27 in the same plate, will be obtained a fair idea of the 

 difference in size between the ordinary dermalia and those in a 

 group around the Hydrozoan body. The paratangentials of the 

 latter kind of dermalia generally lie somewhat below the general 



